The aim of this study is two fold. First is to develop genealogical resources to allow advanced studies of the heritability of disorders in the Old Order Amish and related Anabaptist sects. These groups are important to study because they are small, well defined population isolates. In addition, they are enthusiastic historians and have excellent printed genealogical records. We have accomplished much of the first goal by building the Amish Genealogy Database (AGDB) and several computational tools to analyze that database including PedHunter. These tools allow us to generate accurate pedigrees for genetic study in a accurate and rapid fashion. The second goal is to study the genetics of heritable disorders in these groups. To that end we have already cloned the genes that are altered in Glycogen storage disease type 6, McKusick-Kaufman syndrome, Amish Nemaline Myopathy, and are currently working on Amish Microcephaly. We have identified the gene alteration in Amish microcephaly, which is a gene that codes for a protein that transports deoxynucleotides into the mitochondria. We have currently developed an animal model for this disorder and we are now testing hypotheses of pathogenesis and possible treatments.